diff options
| author | Chuck Ebbert <76306.1226@compuserve.com> | 2005-09-09 13:10:15 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-09 14:03:43 -0700 |
| commit | af97c7220a0376beed827e72e3bb27731af7109d (patch) | |
| tree | dae9462270cf9345184b23c95fedbe0fb414514b | |
| parent | ddb99f3d35b178f0715aab2f9d9ab25f61814347 (diff) | |
[PATCH] docs: fix misinformation about overcommit_memory
Someone complained about the docs for vm_overcommit_memory being wrong.
This patch copies the text from the vm documentation into procfs.
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | Documentation/filesystems/proc.txt | 42 |
1 files changed, 32 insertions, 10 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 5024ba7a592..d4773565ea2 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1241,16 +1241,38 @@ swap-intensive. overcommit_memory ----------------- -This file contains one value. The following algorithm is used to decide if -there's enough memory: if the value of overcommit_memory is positive, then -there's always enough memory. This is a useful feature, since programs often -malloc() huge amounts of memory 'just in case', while they only use a small -part of it. Leaving this value at 0 will lead to the failure of such a huge -malloc(), when in fact the system has enough memory for the program to run. - -On the other hand, enabling this feature can cause you to run out of memory -and thrash the system to death, so large and/or important servers will want to -set this value to 0. +Controls overcommit of system memory, possibly allowing processes +to allocate (but not use) more memory than is actually available. + + +0 - Heuristic overcommit handling. Obvious overcommits of + address space are refused. Used for a typical system. It + ensures a seriously wild allocation fails while allowing + overcommit to reduce swap usage. root is allowed to + allocate slighly more memory in this mode. This is the + default. + +1 - Always overcommit. Appropriate for some scientific + applications. + +2 - Don't overcommit. The total address space commit + for the system is not permitted to exceed swap plus a + configurable percentage (default is 50) of physical RAM. + Depending on the percentage you use, in most situations + this means a process will not be killed while attempting + to use already-allocated memory but will receive errors + on memory allocation as appropriate. + +overcommit_ratio +---------------- + +Percentage of physical memory size to include in overcommit calculations +(see above.) + +Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100) + + swapspace = total size of all swap areas + physmem = size of physical memory in system nr_hugepages and hugetlb_shm_group ---------------------------------- |